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Is Black Rice Healthier?

Most of us are familiar with brown, white and “wild” rice. But, how about black-purple rice? Have you tried it yet? Are you interested in it because of the positive media coverage from the likes of Dr. Oz? By the end of today’s column, you’ll likely know more about it and you can decide for yourself if it’s something you ought to add to your diet.

Let’s begin with a few of the positives and a negative of this so-called “forbidden rice”. The natural pigments which give black rice its distinctive color are a class of antioxidants known as anthocyanins. Recent studies indicate that frequent anthocyanin consumption may reduce elevated systemic inflammation and insulin resistance. These purple powerhouses also interfere with sugar absorption and digestion. This may be especially helpful when eating carbohydrate-rich foods such as rice. In addition, at least one study found that black rice is lower in several dangerous elements – arsenic, cadmium, lead and mercury. On the other hand, black-purple rice is higher in iron, an essential mineral. In terms of downsides, the primary issue is cost. Many years ago in China, black rice was referred to as forbidden rice because it was only served to the emperor. Nowadays, farmers in the East and West are cultivating it on a much larger scale for the general population. However, it’s still much more scarce than common forms of rice and, therefore, comes with a heftier price tag.

Thus far, the research conducted on black rice has mostly been carried out in animal models of disease. What’s more, many of the studies have utilized anthocyanin extracts from black rice (AEBR) rather than examining it as a whole grain food source. The results of the published trials reveal that AEBRs improve various aspects of cardiovascular health in lab rabbits and rats. Namely, it has been shown to: positively shift lipid profiles (elevating HDL cholesterol while lowering LDL cholesterol and triglycerides), reduce the formation of atherosclerotic plaques and platelet hyperactivity (a risk factor for blood clots). Currently, only a few human trials involving black rice are available for review. A 2008 study in the journal Nutrition Research reports that meals containing a mixture of black and brown rice are superior to white rice with regard to changes in HDL (“good”), LDL (“bad”) cholesterol, triglycerides and oxidative stress markers. The second study, from 2007, concluded that a black rice fraction “could exert cardioprotective effects on patients with CHD (coronary heart disease) by improving antioxidant status and inhibiting inflammatory factors”.

My stance on black rice is pretty straightforward: If I were to eat rice, which I typically don’t, I would opt for a small serving of organic black rice. It appears to be marginally more nutritious, possibly safer in terms of heavy metal contamination, and possess higher antioxidant activity than other forms of rice. And, although it is relatively high in carbohydrates, its effect on blood sugar is probably mitigated to some extent by the anthocyanin interaction. Having said this, I’m in no rush to add black rice to my own diet. If more human studies are published which suggest real world health benefits, then I would consider supplementing with a black rice extract that is standardized for cyanidin-3-glucoside, a specific anthocyanin with a reasonably strong scientific track record. Such products are already on the market, but will remain off of my supplement shelf until more promising research is available. In the meantime, I’ll get my daily dose of anthocyanins by eating organic berries and drinking organic hibiscus tea and red wine.

Note: Please check out the “Comments & Updates” section of this blog – at the bottom of the page. You can find the latest research about this topic there!

To learn more about the studies referenced in today’s column, please click on the following links:

Study 1 -Intakes of Anthocyanins and Flavones Are Associated with Biomarkers … (link)

11 Comments & Updates to “Is Black Rice Healthier?”

My mother-in-law and wife really enjoy it as well. Mom makes it with chicken broth and several dry and fresh herbs. My wife reports that it’s delicious – similar in taste to brown and white rice, but a bit more al dente.

One day, I’ll give a try myself. Right now, I’m completely avoiding grains of all types.

Effects of four different cooking methods on anthocyanins, total phenolics and antioxidant activity of black rice.

BACKGROUND:

Two cultivars of black rice were investigated for the effects of different cooking methods on anthocyanins, total phenolic compounds and antioxidant activities.

RESULTS:

There was a significant loss of anthocyanins during cooking: roasting resulted in the greatest decrease (94%), followed by steaming (88%), pan-frying (86%) and boiling (77%). Contents of phenolic compounds decreased drastically after cooking, with significantly lower retention in the black rice cultivar that had higher amylose content. DPPH radical-scavenging activity of black rice decreased after cooking. In contrast, metal-chelating activity increased significantly after cooking. Anthocyanins showed a high positive correlation with total phenolic compounds (r2 = 0.936) but a significant negative correlation with metal-chelating activity (r2 = 0.6107).

CONCLUSION:

The results indicate that cooking degraded anthocyanins and other phenolic compounds, but with a concomitant increase in phenolics from possible degradation of anthocyanins, which resulted in the enhancement of metal-chelating activity.

Characterization of total antioxidant capacity and (poly)phenolic compounds of differently pigmented rice varieties and their changes during domestic cooking.

In the recent years, the pigmented rice varieties are becoming more popular due to their antioxidant properties and phenolic content. In this study, we characterized the antioxidant capacity (TAC) and the phenolic profile in white, red and black rice varieties, and evaluated the effect of two cooking methods (i.e. “risotto” and boiling) on these compounds. Before the cooking, all the varieties contained several phenolic acids, whereas anthocyanins and flavonols were peculiar of black rice and flavan-3-ols of red rice. Among the rice varieties, the black had the highest TAC value. The content of (poly)phenolic compounds and TAC decreased after cooking in all three varieties, but to a lesser extent after the risotto method. As a consequence, the risotto cooking, which allows a complete absorption of water, would be a good cooking method to retain (poly)phenolic compounds and TAC in pigmented and non-pigmented whole-meal rice.

From rice bag to table: Fate of phenolic chemical compositions and antioxidant activities in waxy and non-waxy black rice during home cooking.

The objectives of this study were to systematically analyze degradation rate of functional substances, such as total phenolic content (TPC), total flavonoid content (TFC), condensed tannin content (CTC), monomeric anthocyanin content (MAC), cyanidin-3-glucoside (Cy3glc), and peonidin-3-glucoside (Pn3glc), as well as antioxidant activities in cooked waxy and non-waxy black rice through different home cooking manners. Results showed that greater phenolics and antioxidant capacities were detected in non-waxy rice rather than waxy one. All processed black rice exhibited significantly (p<0.05) lower TPC, TFC, CTC, MAC, Cy3glc, Pn3glc, and antioxidants as compared to the raw rice. Different processing methods significantly degraded the content and activities of antioxidants of both waxy and non-waxy black rice. Under the same cooking time, black rice porridge retained more active substances than that of cooked rice by rice cooker. Therefore, to maintain bioavailability of active components, black rice porridge may gain more health promoting effects.

The Glycemic Potential of White and Red Rice Affected by Oil Type and Time of Addition.

Limited research exists on how different oil types and time of addition affect starch digestibility of rice. This study aimed to assess the starch digestibility of white and red rice prepared with 2 oil types: vegetable oil (unsaturated fat) and ghee (clarified butter, saturated fat) added at 3 different time points during the cooking process (“before”: frying raw rice in oil before boiling, “during”: adding oil during boiling, and “after”: stir-frying cooked rice in oil). Red rice produced a slower digestion rate than white rice. White rice digestibility was not affected by oil type, but was affected by addition time of oil. Adding oil “after” (stir-frying) to white or red rice resulted in higher slowly digestible starch. Red rice cooked using ghee showed the lowest amount of glucose release during in vitro digestion. The addition of ghee “during” (that is boiling with ghee) or “before” (that is frying rice raw with ghee then boiling) cooking showed potential for attenuating the postprandial glycemic response and increasing resistant starch content. This is the first report to show healthier ways of preparing rice. White rice with oil added “after” (stir-fried) may provide a source of sustained glucose and stabilize blood glucose levels. Boiling red rice with ghee or cooking red rice with ghee pilaf-style may provide beneficial effects on postprandial blood glucose and insulin concentrations, and improve colonic health. The encouraging results of the present study justify extending it to an in vivo investigation to conclusively determine the effect of time of addition of fat when rice is cooked on blood glucose homeostasis.

Determination of contents and antioxidant activity of free and bound phenolics compounds and in vitro digestibility of commercial black and red rice (Oryza sativa L.) varieties.

Black and red rices (Oryza sativa L.) were analysed for total flavonoids and phenolics and the HPLC profile including both free and bound phenolic fractions. Moreover, antioxidant activity and in vitro digestibility was determined. Content of flavonoids and polyphenols as well as antioxidant activity was higher in free phenolic fractions. Bound flavonoids in black rices were not significant contributors to antioxidant activity. The main free phenolics in black rices were ferulic, protocatechuic and trans-p-coumaric acids, while the major free phenolics in red rices were catechin, protocatechuic and caffeic acids. The main bound phenolics in black rices were ferulic and vanillic acids and quercetin, in red rice types, they were ferulic, syringic, trans-p-coumaric acids and quercetin. Newly, the presence of m-coumaric acid in red rices was detected. Steam cooked rices showed very high levels of organic matter digestibility, whereas red rices were significantly more digestible than black rices (p<0.05).

Correlation Between Phytochemical and Mineral Contents and Antioxidant Activity of Black Glutinous Rice Bran, and Its Potential Chemopreventive Property.

In this work total anthocyanin content (TAC), total flavonoid content (TFC), total phenolic content (TPC) and minerals found in five black glutinous rice cultivars (MS, SK, PY, PC and KK) from Thailand were analyzed. The antioxidant activity of anthocyanin-rich black glutinous rice bran extracts against nitric oxide radical (NO˙), superoxide radical (O2˙Ż) and lipid peroxyl radical (LOO˙) was also determined. Potential chemopreventive property of rice bran extract was screened based on cellular bioassays for phase II detoxification enzyme induction. Quinone reductase (QR) induction in murine hepatoma cells was used as a marker for this effect. Rice bran extract of cultivar KK had the highest TAC, of SK the highest TFC and of PC the highest TPC. The best antioxidants against NO˙, O2˙Ż and LOO˙ were cultivars KK, MS, and SK, respectively. Overall, TAC, TFC and TPC had a combinatorial effect on the antioxidant activities of all extracts; none of them dominated. Minerals may not play a role in the antioxidant activity of the extracts because most correlations between them and the antioxidant activity were unpredictable. However, rice bran contained high mass fractions of some essential minerals on dry mass basis, including Zn (103-133 µg/g), Se (11-18 µg/g) and Cu (3.8-7.1 µg/g). Chemopreventive study indicated that PC cultivar was the most potent chemopreventor with the lowest concentration of an inducer needed to double the QR activity (CD value) of 0.7 µg/mL. These findings showed that black glutinous rice bran is rich in phytochemicals and some essential minerals, and has a potential chemopreventive property.

Evaluation of phenolic profile and antioxidant capacity in gluten-free flours.

The characterization of phenolic fingerprints in common gluten-free flours is still scarce. Total phenolic and anthocyanin contents, antioxidant capacity and the entire phenolic profile were investigated for extracts from chickpea, sorghum, quinoa, black rice, lentil, amaranth, brown rice, oat and white rice flours, using soft wheat flour as a comparison. The highest phenolic content was found in black rice, followed by quinoa extracts (147.9 and 87.2mg gallic acid equivalents 100g-1, respectively). Consistently, antioxidant capacity was highest in black rice and quinoa flours (34mmol trolox equivalents 100g-1), while anthocyanins were highest in black rice flour. Data showed a high correlation between phenolic content and both reducing and scavenging activities, with Pearson’s coefficient of 0.90 and 0.91, respectively. Although the entire phenolic profile was diverse and differed among flours, these represent a valuable source of health-promoting compounds, mainly belonging to flavonoids, phenolic acids and lignans.

Be well!

JP

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